Blender 2.83, was sculpting and suddenly my smoothing brush stopped working
In the Properties sidebar, go to Stroke &gt; Stabilize Stroke and turn it off.
Stabilize Stroke basically drags the &quot;actual&quot; brush behind your cursor when sculpting. This results in a red line indicating the distance the actual brush is from the cursor. I do believe this red line is resulting from Stabilize Stroke.